The chemical determination of vitamin A in the blood has been simplified so that it can be carried out in any clinical laboratory. Apart from the changes of the plasma vitamin A in nutritional vitamin A deficiency there are well defined variations of the plasma vitamin A content in many diseases. These variations, not related to nutritional deficiency, appear more interesting since secondary, conditioned1 or endogenous2 vitamin deficiencies (due to processes within the organism) are as significant in medical practice as primary or exogenous due to reduced nutritional intake. Two questions arise: 1. What determines the plasmavitamin A level? 2. How may a knowledge of this level be useful to the clinician?
We attempt to answer these questions on the basis of information gained from the literature and from observations on 2,673 vitamin A determinations on 454 patients.
In a statistical evaluation a t value3 of 2.5
POPPER H, STEIGMANN F. THE CLINICAL SIGNIFICANCE OF THE PLASMA VITAMIN A LEVEL. JAMA. 1943;123(17):1108–1114. doi:10.1001/jama.1943.02840520024007